One of O’Brien’s techniques throughout the book–or at least, one assigned to at least one of his writers–has been to illustrate the show versus tell instruction.
On his smallest finger Orlick screwed the cap of his Waterman fountain-pen, the one with the fourteen-carat nib; when he unscrewed it again there waas a black circle about his finger.
Symbolism of the foregoing: annoyance. (p. 282)
By inserting an "author’s" note below a statement, he is telling us what he is showing. On our own, we would have picked up Orlick’s annoyance at being interrupted in his writing by his fiddling with the pen cap. These "notes" appear as if the author jogged them down to himself. Neatly done.
Getting towards the end of the book–which story though, I’m not quite sure–and the author Trellis is on trial and being judged by a panel and jury of his characters. It seems their complaints are of what he has made them be and represent. From Slug Willard:
In what manner were you compelled to address Mr. Furriskey?
In guttersnipe dialect, at all times repugnant to the instincts of a gentleman.
You have already said that the character or milieu of the conversation was distasteful to you?
Yes. It occasioned considerable mental anguish. (p. 285)
I’m reminded of Kurt Vonnegut’s 8 rules of writing, brought up recently by his death. Included was this, at No. 1: "Use the time of a total stranger in such a way that he or she will not feel the time was wasted."
O’Brien is making this rule even more emphatic; clearly, don’t piss them off.